Abstract
In the field of semiconductor manufacturing, there has been a strong need for non-contact wafer handling since contact can damage the wafer or can generate particles, which cause defective of semiconductor elements. In the past studies, electrostatic levitation was proposed and applied for 200mm and 300mm wafers. In those studies, three degrees of freedom of a wafer were actively controlled to achieve non-contact levitation. However, it seems difficult to levitate larger wafers using the same control scheme, since larger wafers exhibit considerably large deformation, which would destabilize the control system. In this paper, to realize non-contact levitation of 400mm silicon wafer, distributed on-off control scheme is introduced. The realized system employs 15 pairs of electrode units, for each of which voltage is independently controlled according to the gap. A 400mm silicon wafer was successfully levitated with the proposed system at an air gap length of 0.30mm and 0.40mm.
